The present invention relates to a symmetrical waveguide coupler in which two identical waveguides are coupled together.
In optical communications systems operating with wavelength multiplex, optical signals of different wavelengths from separate sources must be combined in one waveguide for transmission. Likewise, in the receiver the signals must be separated again from one another. Full duplex operation using one optical waveguide for both directions also requires such multiplexers, but in this case they serve as transmit-receive duplexers.
Multiple utilization of a transmission medium with different carrier frequency signals in frequency multiplex is also applicable for microwaves, in which case multiplexers and demultiplexers or transmit-receive duplexers, respectively, are then required for the respective microwaves.
For single-mode fiber systems, the multiplexers and demultiplexers should be designed as simply as possible from planar waveguides so that they are suitable for integrated optical systems. For microwaves, particularly those of millimeter wavelength, dielectric waveguides or image guides are suitable for a planar structure.